Method of and appratus for positive fluid flow extrusion

ABSTRACT

Method of and apparatus for extruding material, e.g., a billet, to form a product, e.g., wire, wherein deformation is accomplished by passing the material within a controlled flow of pressurized fluid, the pressure of which deforms the material. Extrusion fluid is injected into the zone of deformation at maximum pressure and at the maximum pressure point for extruding material under controlled conditions to form a product.

United States Patent Cartwright et a1.

[45] July 18, 1972 [54] METHOD OF AND APPRATUS FOR POSITIVE FLUID FLOW EXTRUSION 72] Inventors: John Sutton Cartwright, Pennington;

Francis Joseph Fuchs, Jr., Princeton Junction, both of NJ.

[73] Assignee: Western Electric Company, Incorporated,

New York, NY.

[22] Filed: Oct. 1, I969 [21] Appl. No.: 862,751

[S2] U.S. Cl ..72/60, 72/45, 72/271, 72/467 [51] Int. Cl. ..B2lc 25/02 [58] Field of Search ..72/60, 253, 467, 43, 45, 271

[56] References Cited UNITED STATES PATENTS 3,344,636 10/1967 Pugh ..72/60 3,415,088 12/1968 Alexander et al.. ...72/60 3,449,935 6/1969 McAllan ...72/60 3,191,413 6/1965 Stulen ..72/467 3,251,214 5/1966 Williamson ..72/351 FOREIGN PATENTS OR APPLICATIONS 19,356 10/1893 Great Britain ..72/60 OTHER PUBLICATIONS Beresnev et al.; Some Problems of Large Plastic Deformation" pp. 26-54, 70-74; 1963; The Macmillian Co., New York; Sci. Lib. No. TA 460 B45.

Primary Examiner-Richard J. Herbst Attorney-W. M. Kain, J. P. I-Ioofnagle, Jr., R. C. Winter and J. Schuman [57] ABSTRACT Method of and apparatus for extruding material, e.g., a billet, to form a product, e.g., wire, wherein deformation is accomplished by passing the material within a controlled flow of pressurized fluid, the pressure of which deforms the material. Extrusion fluid is injected into the zone of deformation at maximum pressure and at the maximum pressure point for extruding material under controlled conditions to form a product.

9 China, 6 Drawing Figures PATENTED mu 8 1912 SHEET 2 BF 5 mimmmlemz 3.677.049

SHEET 5 0F 5 METHOD OF AND APPRATUS FOR POSITIVE FLUID FLOW EXTRUSION CROSS REFERENCE TO RELATED APPLICATIONS BACKGROUND OF THE INVENTION This invention relates to methods of and apparatus for the extrusion of a material to form a product.

A recent advance in the extrusion art has been the development of a method for extruding a material, e.g., a billet, to form a product, e.g., wire, wherein deformation is accomplished by passing the material within a controlled flow of pressurized fluid, the pressure of which deforms the material.

Considering briefly such an extrusion method, viz., the method disclosed in the above-referenced co-pending application, a billet of material to be deformed is positioned within the bore of a pressure vessel so as to be immersed in a pressure transmitting medium, e.g., a fluid such as castor oil. A ram having a deforming agency including a fluid control element mounted on the leading end thereof is advanced into the bore to pressurize the fluid and billet material sufficiently to establish a combined flow of fluid and billet material out of the pressure vessel through a shaped passage in the fluid control element. The passage in the fluid control element is shaped to converge in such a manner that the pressure of fluid flowing therethrough, while generally decreasing, is controlled to be at sufficient magnitude to deform the billet material progressively throughout the length of the shaped passage to form the product. The surface of the shaped passage thus defines a flow control surface for controlling the passage of the fluid flowing through the passage in the fluid control element so as to maintain the pressure at sufficient magnitude to deform the billet material passing concurrently therethrough.

With respect to specific flow control surface configurations, the above-noted co-pending application discloses that the flow control surface can be conical having a selectively linear or non-linear profile. Further, it is disclosed therein that the suitable shapes of the flow control surface may be determined by experiment or by other empirical approaches. In this regard, actual extrusion of billet material to form wire has been accomplished with flow control surfaces having linear profiles as well as with flow control surfaces having non-linear profiles.

The method of the above-noted co-pending application has proven to be highly successful in extruding billet material to form a product such as wire. The method and apparatus of the present invention, however, have been found to provide improved results in positive fluid flow extrusion by insuring that deformation of the billet material occurs totally within the confines of the fluid control element thereby providing positive control of the deformation of the material at all times during extrusion.

As is disclosed in the above-mentioned co-pending application, the positive fluid flow defonnation of material to form a product is accomplished by exerting controlled fluid pressures on the material, the magnitudes of which pressures are such as to generate radial stresses therein which are in excess of the generated axial stresses by an amount equal to the yield stress of the material. It has been found, however, that because of the work-hardening characteristics of some materials, the radial and axial stress relationship necessary to support deformation requires a maximum pressure to be exerted on the surface of the deforming billet material at a point therealong downstream from the point of initial deformation. Thus, with respect to these materials, deformation occurs both upstream and downstream from the point of maximum pressurization.

As also is disclosed in the above-referenced co-pending application, the high pressure point experienced during extrusion in accordance with the method thereof occurs at the leading edge of the advancing fluid control element. Thus, with respect to materials having work hardening characteristics which cause maximum pressure to be exerted subsequent to initial deformation, the initial deformation of such materials in the apparatus disclosed in the co-pending application will be upstream of and therefore outside the confines of the fluid control element. This, although generally acceptable, does not provide the maximum positive control which would be achievable if deformation could occur totally within the confines of the fluid control element, notwithstanding the work hardening characteristics of the material being deformed.

SUMMARY OF THE INVENTION It is an object of this invention, therefore, to provide a method of and apparatus for the positive fluid flow extrusion of a material to form a product wherein the deformation of the material occurs substantially totally within a fluid control element.

This object is accomplished by the method of the present invention which may include the steps of injecting fluid intermediate the ends of a passage in a fluid control element to establish a flow of pressurized fluid along a flow control surface defined by the surface of the passage, passing the material to be deformed within the flow of pressurized fluid and extruding the material as the material passes within the flow by the exertion of pressure thereon by the flowing pressurized fluid.

Apparatus according to the invention may comprise a deforming agency including a controlled flow of pressurized fluid flowing within a passage formed in a fluid control element, means for injecting fluid intermediate the ends of said passage to establish said controlled flow of pressurized fluid and means for establishing a relative velocity between the material and the deforming agency to cause the material to pass within the flow of pressurized fluid to extrude the material by the exertion of pressure thereon by the flowing pres surized fluid.

A fluid control element according to the invention may include a body having a longitudinally axially extending passage formed therein, at least a portion of the surface of the passage being shaped to control a flow of fluid, and means intermediate the ends of the passage to accommodate the introduction of fluid within the passage.

BRIEF DESCRIPTION OF THE DRAWINGS A more complete understanding of the present invention may be had from the following detailed description, particularly when considered in the light of the accompanying drawings wherein:

FIG. I is a plot of extrusion fluid pressure and material yield stress vs. billet radius as the material is deformed according to the invention;

FIG. 2 is a partial cross-sectional view of an extrusion apparatus according to the invention;

FIG. 3 is a partial cross-sectional view of an adjoining portion of the apparatus of FIG. 2;

FIG. 4 is a plot plan showing the relationship between FIGS. 2 and 3;

FIG. 5 is a partial cross-sectional view similar to FIG. 3 but showing the position of the apparatus elements at the completion of the deformation of the billet material; and

FIG. 6 is an expanded, partial cross-sectional view of the fluid control element of the apparatus of FIGS. 2, 3 and S during deformation.

DETAILED DESCRIPTION It has been found that in deforming materials by passing the material to be deformed within a controlled flow of pressurized fluid, the pressure of which fluid against the material causes deformation thereof, the maximum pressure necessary to maintain deformation may be required to be exerted against the material at some point intermediate the point of commencement and the point of termination of the deformation.

This phenomenon results from the change in work hardening characteristics of the material being deformed.

More specifically, it was noted above with respect to the above-referenced co-pending application that positive fluid flow deformation of material to form a product is accomplished by exerting controlled fluid pressures on the material, the magnitudes of which pressures are such as to generate radial and axial stresses in the material such that the radial stresses are in excess of the axial stress by an amount equal to the yield stress of the material. It has been found, however, that initial deformation of some materials causes a rapid increase in the yield stress of the material. In fact, the increase in the yield stress of the material is such as to preclude further material deformation in the absence of an increase in the pressure of the deforming or extrusion fluid.

A better understanding of the manner in which some materials react during positive fluid flow extrusion can be had with reference to FIG. 1 which presents a plot of extrusion fluid pressure during the extrusion of a billet, as well as a plot of yield stress of the material of the billet during deformation of the material from a radius of 0.180 inches to a radius of 0.0225 inches. The yield stress curve, which relates to an aluminum alloy (EC Alum.) and which was developed by actual measurement of the yield stress of the deformed head end of a billet of material, shows a rapid rate of increase of yield stress at the beginning of deformation, with a gradual flattening of the curve thereafter. The increase in yield stress is such as to require an initially increasing extrusion fluid pressure in order to maintain extrusion. The increased extrusion fluid pressure requirement is reflected in the plot of extrusion fluid pressure, which curve presents calculated values of the extrusion fluid pressure based upon the extrusion of a billet of EC. Alum., 0.360 inches in diameter to form a product 0.045 inches in diameter, using castor oil with weight percent molybdenum disulfide (MnS,) as extrusion fluid.

The extrusion fluid pressure curve is defined by Sy, is the yield stress of the material at the upstream end of an increment of material being deformed;

Y, is the radius at the upstream end of an increment of material being deformed;

Y, is the radius at the downstream end of an increment of material being deformed;

P is the pressure of the extrusion fluid at the upstream end of an increment of material being deformed;

P, is the pressure of the extrusion fluid at the downstream end of an increment of material being deformed;

S, is the axial stress in the material being deformed at the downstream end of an increment thereof; and

0 is the angle subtended by the surface of the increment of material being deformed with the longitudinal axis of the fluid control element in which the material is being deformed.

In plotting the extrusion fluid pressure curve of H6. 1, the surface angle 6 was assumed to be constant at all points during deformation except for the area of initial entry of the material into the zone of deformation. in this area of initial entry, the angle 0 was varied from 0 at the point of initial entry to a value of at an arbitrary point within the zone of deformation whereafter the angle 6 was maintained for calculation purposes at a constant 20.

As is evident from the curve, the pressure of the extrusion fluid has a maximum value intermediate the beginning and end points of deformation. The longitudinal position of this point within the zone of deformation is also quite clearly defined. Specifically, it was noted above that the angle 0 ofthe surface of the deforming material is constant upstream of the exit end of the zone of deformation to an arbitrary point at which the angle is reduced arbitrarily to 0". The arbitrary point may be at the high pressure point or further upstream. Because of the conical shape of the material surface between the high pressure point and the exit end of the zone of deformation, a cross-sectional view of the material being deformed provides a right triangle having as the hypotenuse the surface of the material from the exit end of the zone of deformation to the high pressure point, as one side a portion of the radius at the high pressure point, and as one angle the surface angle 0. it being evident from the curve that the high pressure point occurs at that point where the billet material has a radius of 0.148 inches, the longitudinal position of the high pressure point can be seen to be a function of the billet radius at that point, viz. the longitudinal distance between the exit of the zone of deformation and the high pressure point within the zone of deformation is equal to the change in radius of the billet between the high pressure point and the exit end of the zone of deformation multiplied by the cotangent of the angle 0.

AS was noted above, the maximum pressure point in positive fluid flow extrusion methods such as that of the abovenoted co-pending application occurs at the leading edge of the advancing fluid control element. In order to have the high pressure generating point and the high pressure point for supporting extrusion coincide, therefore, a portion of the deformation occurs upstream from the confines of the fluid control element and is not positively controlled in the sense that posi tive control occurs when the extrusion fluid flow during deformation is confined by a pre-shaped flow control surface.

The present invention provides for substantially totally containing the material being deformed within the fluid control element and positively controlling the pressure and flow of the extrusion fluid at all times during deformation of material by injecting the extrusion fluid into the zone of deformation at a point within the fluid control element corresponding to the point of maximum required pressure. Thus, with the curve of extrusion fluid pressure in FIG. I, the point within the zone of deformation at which maximum pressure occurs is defined and, in practicing the invention, extrusion fluid at the maximum pressure is injected at that point to flow both upstream and downstream therefrom to provide fluid at a pressure along the surface of the deforming material which corresponds to the pressure shown in FIG. 1.

An apparatus according to the invention, designated generally by the reference numeral 10, is shown in FIGS. 2 and 3 which should be considered together.

Apparatus 10 comprises a pressure vessel ll having an inner bore 12 which is closed at one end by a sealed plug 13 (FIG. 5). The closed end 13 of vessel 11 is rigidly mounted on a base 14 (FIG. 5) by a suitable means (not shown) such as bolts or the like.

Formed intermediate the ends of bore 12 is an annular shoulder 15 having a seal provided in an annular channel formed in the inner surface of the shoulder. Sealed shoulder 15 separates bore 12 into an upstream portion 16 (to the right as seen in FIGS. 2 and 3) and a downstream portion 17.

Telescopically received within the downstream portion 17 of bore 12 through the open end of vessel ll is a generally cylindrical ram 18. Advancement of ram 18, schematically indicated by arrows 20, is accomplished by a press or other suitable mechanism (not shown) known to those in the art. Formed in the vessel-adjacent end of ram 18 is a threaded counterbore 21 for receiving a fluid control element 22 therein. Also formed in ram 18 is a longitudinally axially extending bore 24 for accommodating therethrough the discharge of product 26 and extrusion fluid after deformation, as is discussed below in detail.

Fluid control element 22 comprises an elongated generally cylindrical body having a longitudinally bore 28 extending axially therethrough. Bore 28 is shown as being equal in diameter to bore 24 of ram 18 and cooperates therewith to define a discharge passage for product 26 and extrusion fluid after deformation. The downstream (left as seen in FIG. 2) end of fluid control element 22 is provided with a threaded boss 29 which is threadedly received within counterbore M of ram 18.

The diameter of the circumferential surface 31 of the major portion of fluid control element 22 is substantially equal tothe diameter of the inner surface of sealed shoulder so as to establish a slidable but sealed relationship therewith. However, a portion 33 of the upstream end of fluid control element 22 is provided with diameters substantially equal to the diameter of upstream portion 16 of bore 12 so as to establish a radi ally fixed but longitudinally slidable relationship therewith. The circumferential surface of upstream portion 33 of fluid control element 22 is provided with a plurality of longitudinally extending grooves which define fluid passages 34 for allowing the free communication of fluid past upstream portion 33.

Formed in the upstream end of the fluid control element 22 is an axially extending, converging generally conical opening, the surface 40 of which defines a flow control surface for controlling the flow of extrusion fluid during extrusion. The volume bounded by the conical opening in fluid control element 22 comprises a zone of deformation 42 within which all deformation of the material of a billet 44 to form a product 26 in the apparatus 10 takes place.

Formed in the flow control surface 40 are a plurality of apertures 45 which communicate the zone of deformation 42 with a plurality of longitudinally extending passages 46 in fluid control element 22. Each passage 46 communicates with a radially extending passage 48 formed in fluid control element 22 to allow the passage of extrusion fluid from around fluid control element 22, through passages 48, 46 and apertures 45 to be injected into the zone of deformation 42. Apertures 45 are located within the zone of deformation to correspond to the longitudinal position therealong where the maximum extrusion fluid pressure is required for accomplishing extrusion of the material to be deformed. For example, the pressure plot of FIG. 1 shows that for an EC Alum. billet having an outside diameter of 0.360 inches, in accomplishing an extrusion ratio of 64:1, the maximum pressure required occurs at a diameter of 0.296 inches. Thus, the longitudinal position of apertures 45 within the zone of deformation 42 of a fluid control element 22 for extruding the billet is determined from the relationship:

(0.l480-0.0225) cotan 6.

The circumferential surface 31 of fluid control element 22 cooperates with the inner surface of downstream bore 17, ram 18 and annular shoulder l5 to define an annular extrusion fluid pumping chamber 50. Extrusion fluid for establishing a positive flow of fluid within zone of deformation 42 is introduced to chamber 50 through a radially extending passage 52 formed in, vessel II which communicates chamber 50 with a source of extrusion fluid (not shown). A fluid line 53 communicating passage 52 with the source of extrusion fluid is provided with a check valve 55 which permits the introduction of fluid to chamber 50 but precludes reverse flow of the fluid when the fluid in chamber 50 is pressurized as is discussed below in detail.

Similarly, the circumferential surface 31 of fluid control element 22 cooperates with the upstream end of shoulder 15, the inner surface of upstream bore 16 and the upstream portion 33 of fluid control element 22 to define a fluid receiving chamber 60 into which fluid passes through grooves 34 during deformation of billet 44. It can be seen from a comparison of FIGS. 2 and 3 with 5 that the advancement of ram 18 and therewith fluid control element 22 causes a reduction in the volume of extrusion fluid pumping chamber 50 and an increase in the volume of fluid receiving chamber 60. The variation in the volumes of these chambers during extrusion provides for a flow of fluid through the zone of deformation during positive fluid flow extrusion according to the invention.

Considering now the operation of the apparatus 10 as shown in FIGS. 2 and 3, with plug 13 (FIG. 5) removed, fluid control element 22 is inserted into bore [2 through the normally closed end of vessel 11 so as to extend through the opening defined by annular shoulder 15 and be threadedly engaged with threaded bore 21 of ram 18. Thereafter, a billet 44 to be extruded is positioned within the upstream portion 16 of bore 12. The head end of the billet may be selectively pre-shaped or not, however, pre-shaping of the billet, e.g. in the manner disclosed in the co-pending application of FJ. Fuchs, Jr. for METHOD OF PREFORMING MATERIALS WHICH WORK-HARDEN, Ser. No. 758,732, filed Sept. 10, I968 and assigned to the same assignee as this application, enhances the operation.

The system having been filled with fluid, plug 13 is threadedly secured within the end of vessel I l and the vessel is thereafler secured to base 14.

The upstream portion 16 of bore [2, the upstream end of fluid control element 22 and plug 13 cooperate to define a material receiving chamber 62 for containing billet 44 and a pressure transmitting medium. Billet 44 is positioned within the chamber 62 such that it is surrounded by the fluid and maintained in spaced relationship with respect to the surface of bore 12.

With billet 44 so positioned, ram 18 and therewith fluid control element 22 is advanced within bore 12 to establish a relative velocity between the billet and the fluid control ele-' ment. Advancement of fluid control element 22 causes an increase in the pressure of fluid in fluid pumping chamber 50 which closes check valve 55, and which further causes the volume of extrusion fluid pumping chamber 50 to decrease, thereby pumping fluid from chamber 50 through passages 48, 46 and apertures 45 for injection into the zone of deformation 42. Fluid entering the zone of deformation through apertures 45 is caused to flow in two directions. Specifically, and with reference to FIG. 6, the fluid entering zone of deformation 42 from passages 46 through apertures 45 splits into an upstream and a downstream flow. The upstream flow of fluid passes between the head of billet 44 and that portion of the flow control surface 40 upstream of apertures 45 to be combined with -the fluid surrounding billet 44 in chamber 62 to pass through grooves 34 and into expanding fluid receiving chamber 60. The remaining fluid flows downstream from apertures 45 between flow control surface 40 and the head end of billet 44 and thereafter passes out of apparatus 10 through passage 24 with extrusion product 26.

It is evident from the foregoing that various volumetric rela tionships are established during the operation of apparatus l0. Specifically, the volume of fluid pumped from extrusion fluid pumping chamber 50 into the zone of deformation 42 is equal to the sum of the upstream and downstream flows of fluid within the zone of deformation. Similarly, the incremental increase in the volume of fluid receiving chamber 60 must equal the volumes of fluid passing upstream within the zone of deformation 42 and displaced from chamber 62 around billet 44 during an incremental advance of fluid control element 22.

The volume of fluid pumped from chamber 50 by an incremental advance of fluid control element 22 and ram 18 will be controlled by the cross-sectional area of extrusion fluid pumping chamber 50, and is determinable from the volume of fluid required to maintain a positive flow of fluid within the zone of deformation 42 for continually deforming the material of billet 44. In this regard, it should be noted that as discussed above, the pressure of the fluid being provided to the zone of deformation 42 is maximum at the point of entry thereto through apertures 45. Thereafter, the pressure decreases both upstream and downstream within the zone of deformation to establish a pressure profile of the fluid across the zone of deformation which increases, for example, to that shown in FIG. I. The absolute quantity of fluid required and the pressure at which fluid will be introduced is dictated by the material being deformed, the extrusion ratio, the characteristics of the pressure transmitting medium and the speed of advance of fluid control element 22. In this regard, the volumes and pressures required for any particular extrusion can be determined empirically. It should be noted, however, that extrusion under ideal conditions and requiring a minimum amount of work may be accomplished by utilizing the apparatus of the invention, contouring flow control surface 40 and providing fluid from extrusion fluid pumping chamber 50 into the zone of deformation in quantifies determined in the manner disclosed in the copending application for METHOD OF AN OP- TIMUM FLUID CONTROL ELEMENT FOR POSITIVE FLUID FLOW EXTRUSION, Ser. No. 862,765, filed Oct. l, I969, which application is assigned to the same assignee as the present application.

It can be seen from the foregoing that the present invention provides for positive fluid flow extrusion wherein extrusion fluid is injected within the zone of deformation through the fluid control element at maximum pressure and at the point of maximum pressure for accomplishing deformation totally within the zone of deformation defined by flow control surface 40. Thus, the invention provides for positive fluid flow extrusion of material to form a product wherein deformation is accomplished under controlled conditions at all times.

Many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood, that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

What is claimed is: l. A method of hydrostatically extruding an elongated workpiece through an extrusion die having an inlet end adapted to receive said elongated workpiece and an outlet end adapted to discharge extruded product, said die having a zone of deformation between said inlet end and said outlet end, said method comprising:

a. introducing a flow of pressurized fluid into the zone of deformation of said extrusion die at a point between the inlet end and outlet end of said extrusion die, b. flowing said pressurized fluid in i. a first stream directed from said point to the inlet end of said extrusion die, said first stream being interposed in the zone of deformation between said elongated workpiece and said die, and

ii. a second stream directed from said point to the outlet end of said die, said second stream being interposed in the zone of deformation between said elongated workpiece and said die, said first and second streams of pressurized fluid completely separating said workpiece and said die and deforming said workpiece in said zone of deformation,

c. the pressure of said fluid in said zone of deformation being a maximum at said point.

2. A method of hydrostatically extruding a billet of material having a butt end and a head end through an extrusion die having an inlet end adapted to receive the head end of said billet of material and an outlet end adapted to discharge extruded material, said die having a zone of deformation between said inlet end and said outlet end, said method comprising:

a. positioning said billet of material in a fluid filled chamber having one end open, the head end of said billet of material facing the open end of said chamber and the butt end of said billet of material facing the closed end of said chamber,

b. advancing said extrusion die inlet end first into said chamber to establish a first flow of pressurized fluid interposed between said head end of said billet of material and the zone of deformation of said extrusion die,

c. introducing a second flow of pressurized fluid into the zone of deformation of said extrusion die at a point between the inlet end and the outlet end of said extrusion die,

d. said first and second flows of pressurized fluid completely separating said billet of material and said zone of deformation, said head end of said billet of material and said zone of deformation cooperating to establish a restriction to said first and second flows of pressurized fluid through the outlet end of said extrusion die during said advancement of said extrusion die, said first and second flows of pressurized fluid deforming said billet of material in said zone of deformation, the advancement of said extrusion die being continued past the point at which extrusion of said billet of material through the said extrusion die commences,

e. restricting flow of pressurized fluid through said restriction from adjacent said butt end of said billet of material to adjacent said head end of said billet of material, whereby advancement of said extrusion die into said chamber urges said billet of material toward the closed end of said chamber thereby to increase the pressure of fluid between the butt end of said billet of material and the closed end of said chamber,

f. continuing said advancement of said extrusion die and said introduction of said second flow of pressurized fluid to maintain said first and second flows of pressurized fluid between said billet of material and said zone of deformation thereby to continue said extrusion of said material through said extrusion die.

3. Apparatus for hydrostatically extruding material comprising:

a. a pressure vessel having a bore therein;

b. an extrusion die mounted for reciprocation within said bore;

c. a zone of deformation extending between the ends of said extrusion die;

d. means for injecting fluid intermediate the ends of said zone of deformation to establish a flow of fluid within said zone of deformation;

. an annular shoulder formed in said bore, said annular shoulder cooperating with said extrusion die and said pressure vessel to define a fluid pumping chamber; and

. at least one fluid passage formed in said extrusion die to accommodate the flow of fluid from said fluid pumping chamber to said zone of deformation.

4. Apparatus according to claim 3 wherein fluid is pumped from said fluid pumping chamber through said fluid passages in response to displacement of said extrusion die toward said material.

5. Apparatus according to claim 3 wherein said bore is closed at one end and further including:

g. a fluid receiving chamber for receiving a portion of said injected fluid after passage thereof out of said zone of deformation.

6. Apparatus according to claim 5 and further including:

grooves formed in the outer surface of said extrusion die for accommodating the entry of said fluid into said fluid receiving chamber.

7. Apparatus for hydrostatically extruding material includlng:

a. a vessel having a bore therein closed at one end;

b. an extrusion die mounted for reciprocation within said bore;

c. an annular shoulder formed on said bore and disposed intermediate the open and closed ends thereof;

d. said vessel, extrusion die and shoulder cooperating to define a fluid pumping chamber;

e. said vessel, extrusion die and shoulder cooperating to define a fluid receiving chamber;

f. said extrusion die and said closed end of said vessel cooperating to define a material receiving chamber;

g. a zone of deformation formed in said extrusion die; and

h. a plurality of fluid passages formed in said extrusion die for communicating said fluid pumping chamber with said zone of deformation, said fluid being pumped from said fluid pumping chamber in response to the advance of said extrusion die toward the closed end of said vessel.

8. Apparatus according to claim 7 wherein a portion of said fluid pumped from said fluid pumping chamber flows into said material receiving chamber.

receiving chamber 

1. A method of hydrostatically extruding an elongated workpiece through an extrusion die having an inlet end adapted to receive said elongated workpiece and an outlet end adapted to discharge extruded product, said die having a zone of deformation between said inlet end and said outlet end, said method comprising: a. introducing a flow of pressurized fluid into the zone of deformation of said extrusion die at a point between the inlet end and outlet end of said extrusion die, b. flowing said pressurized fluid in i. a first stream directed from said point to the Inlet end of said extrusion die, said first stream being interposed in the zone of deformation between said elongated workpiece and said die, and ii. a second stream directed from said point to the outlet end of said die, said second stream being interposed in the zone of deformation between said elongated workpiece and said die, said first and second streams of pressurized fluid completely separating said workpiece and said die and deforming said workpiece in said zone of deformation, c. the pressure of said fluid in said zone of deformation being a maximum at said point.
 2. A method of hydrostatically extruding a billet of material having a butt end and a head end through an extrusion die having an inlet end adapted to receive the head end of said billet of material and an outlet end adapted to discharge extruded material, said die having a zone of deformation between said inlet end and said outlet end, said method comprising: a. positioning said billet of material in a fluid filled chamber having one end open, the head end of said billet of material facing the open end of said chamber and the butt end of said billet of material facing the closed end of said chamber, b. advancing said extrusion die inlet end first into said chamber to establish a first flow of pressurized fluid interposed between said head end of said billet of material and the zone of deformation of said extrusion die, c. introducing a second flow of pressurized fluid into the zone of deformation of said extrusion die at a point between the inlet end and the outlet end of said extrusion die, d. said first and second flows of pressurized fluid completely separating said billet of material and said zone of deformation, said head end of said billet of material and said zone of deformation cooperating to establish a restriction to said first and second flows of pressurized fluid through the outlet end of said extrusion die during said advancement of said extrusion die, said first and second flows of pressurized fluid deforming said billet of material in said zone of deformation, the advancement of said extrusion die being continued past the point at which extrusion of said billet of material through the said extrusion die commences, e. restricting flow of pressurized fluid through said restriction from adjacent said butt end of said billet of material to adjacent said head end of said billet of material, whereby advancement of said extrusion die into said chamber urges said billet of material toward the closed end of said chamber thereby to increase the pressure of fluid between the butt end of said billet of material and the closed end of said chamber, f. continuing said advancement of said extrusion die and said introduction of said second flow of pressurized fluid to maintain said first and second flows of pressurized fluid between said billet of material and said zone of deformation thereby to continue said extrusion of said material through said extrusion die.
 3. Apparatus for hydrostatically extruding material comprising: a. a pressure vessel having a bore therein; b. an extrusion die mounted for reciprocation within said bore; c. a zone of deformation extending between the ends of said extrusion die; d. means for injecting fluid intermediate the ends of said zone of deformation to establish a flow of fluid within said zone of deformation; e. an annular shoulder formed in said bore, said annular shoulder cooperating with said extrusion die and said pressure vessel to define a fluid pumping chamber; and f. at least one fluid passage formed in said extrusion die to accommodate the flow of fluid from said fluid pumping chamber to said zone of deformation.
 4. Apparatus according to claim 3 wherein fluid is pumped from said fluid pumping chamber through said fluid passages in response to displacement of said extrusion die toward said material.
 5. Apparatus according to claim 3 wherein said bore is closed at one end and further includiNg: g. a fluid receiving chamber for receiving a portion of said injected fluid after passage thereof out of said zone of deformation.
 6. Apparatus according to claim 5 and further including: grooves formed in the outer surface of said extrusion die for accommodating the entry of said fluid into said fluid receiving chamber.
 7. Apparatus for hydrostatically extruding material including: a. a vessel having a bore therein closed at one end; b. an extrusion die mounted for reciprocation within said bore; c. an annular shoulder formed on said bore and disposed intermediate the open and closed ends thereof; d. said vessel, extrusion die and shoulder cooperating to define a fluid pumping chamber; e. said vessel, extrusion die and shoulder cooperating to define a fluid receiving chamber; f. said extrusion die and said closed end of said vessel cooperating to define a material receiving chamber; g. a zone of deformation formed in said extrusion die; and h. a plurality of fluid passages formed in said extrusion die for communicating said fluid pumping chamber with said zone of deformation, said fluid being pumped from said fluid pumping chamber in response to the advance of said extrusion die toward the closed end of said vessel.
 8. Apparatus according to claim 7 wherein a portion of said fluid pumped from said fluid pumping chamber flows into said material receiving chamber.
 9. Apparatus according to claim 7 and further including grooves formed in the outer surface of said extrusion die to communicate said fluid receiving chamber with said material receiving chamber. 